Diaporthe angustiapiculata Senan., sp. nov.
Index Fungorum number: IF 900439; MycoBank number: MB 900439; Facesoffungi number: FoF 14191; Fig. 1.
Etymology – based on the narrowed apex of conidiogenous cells.
Saprobic on petiole of Phoenix roebelenii O’Brien. Sexual morph: Undetermined. Asexual morph: Conidiomata 375–520 × 580–610 µm ( x = 500 × 600 µm, n=10), superficial, scattered on substrate, solitary, compressed subglobose, dark brown, coriaceous, ostiolate, papillate. Conidiomatal wall comprises pale brown, thick-walled, cells of textura angularis. Conidiophores reduce to conidiogenous cells. Alpha conidiogenous cells 19–27×4–6 µm (x=25×5 µm), phialidic, terminal, bottleshaped with narrowed apex, no visible periclinal thickening, straight, aseptate, unbranched, densely aggregated, hyaline, thick-walled. Alpha conidia 6–9×3–5 µm (x=7×4.5 µm), lower end round, upper end pointed, aseptate, distinct biguttulate, hyaline. Beta conidia not observed.
Culture characteristics – Colonies on PDA reaching 3 cm diam. after 10 days in dark at 25 °C, floccose, flat, circular, entire margin, white, wooly aerial mycelia, reverse off-white, no pigments produced.
Material examined – China, Guangdong Province, Guangzhou City, Danxia Mountain, on petiole of Phoenix roebelenii (Arecaceae), 23 September 2021, I.C. Senanayake, 2R (MHZU 22-0110, holotype), ex-type cultures ZHKUCC 22-0184, ZHKUCC 22-0194.
GenBank numbers – ITS: OR164920, OR164921, tef1-α: OR166269, OR166270, β-tubulin: OR166309, OR166310, calmodulin: OR166299, OR166300.
Notes – The combined gene analysis of ITS, β-tubulin, tef1-α and cal (Fig. 2) shows that our isolates (ZHKUCC 22-0184, ZHKUCC 22-0194) grouped with Diaporthe apiculatum, D. gardeniae, D. charlesworthii which is basal to D. eres species complex with ML/BI=93%/0.99 bootstrap support. The base pair differences of ITS, β-tubulin, and tef1-α locus between our isolates and D. apiculatum revealed that 1.69%, 10.27%, 12.46%, and for D. gardeniae are 3.7%, 13.5%, N/A, while these differences for D. charlesworthii are 3.5%, 5%, 12% respectively. Phylogenetic network from the concatenated dataset based on the LogDet transformation and the NeighborNet algorithm, inferred by SplitsTree shows that our isolates do show any recombination with the species members in the Diaporthe eres species complex and other well-delimitated species (Fig. 3c).
Figure 1 – Diaporthe angustiapiculata (MHZU 22-0110, holotype). a Conidiomata on substrate. b Cross section of conidioma. c, d Conidia attached to conidiogenous cells. e Surface view of colony on PDA. f Reverse view of colony on PDA. Scale bars: b=250 µm, c, d=20 µm
Figure 2 – Phylogram generated from maximum likelihood analysis based on combined ITS, β-tubulin, tef1-α and cal sequence data which comprised 1801 characters (ITS=590, β-tubulin=399,tef1-α=401, cal=411). The best scoring RAxML tree with a final likelihood value of − 66,138.215080 is presented. The matrix had 1373 distinct alignment patterns, with 21.86% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.220620, C=0.327829, G=0.221919, T=0.229632; substitution rates: AC=1.155068, AG=3.569724, AT=1.178946, CG=0.924185, CT=4.411577, GT=1.0; gamma distribution shape parameter α=0.524319. Bootstrap support for maximum likelihood (ML) equal to or greater than 50% and clade credibility values greater than 0.90 (the rounding of values to 2 decimal proportions) from Bayesian inference analysis are labelled at each node. Ex-type strains are in bold, while the new isolate is indicated in blue bold. Except D. arecae species complex, other all species complexes are compressed. The tree is rooted to Cytospora disciformis (CBS 116827) and C. leucostoma (SXYLt)
Figure 3 – Phylogenetic network from the concatenated data (ITS, β-tubulin, tef1-α, cal) representing the structure of the a Diaporthe arecae, c D. eres species complexes and other well-delimitated species b the newly generated Diaporthe strains, based on the LogDet transformation and the NeighborNet algorithm, inferred by SplitsTree. The scale bar represents the expected number of substitutions per nucleotide position